Water jet type pump and method for operation thereof

ABSTRACT

A water jet type pump is part of a system for generating an ultrahigh vacuum. The pump includes a pump chamber through which an ionic fluid flows at high velocity. The chamber has a first fluid feed for the fluid, the first feed ending in a nozzle with a nozzle opening, and a fluid discharge. A second feed of the pump chamber is connected to a high pressure chamber to be evacuated. Gas is suctioned out of the high vacuum chamber through the second feed by way of the flowing fluid jet, which is used to discharge the gas out of the pump chamber.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and hereby claims priority to International Application No. PCT/EP2009/054320 filed on Apr. 9, 2009 and German Application No. 10 2008 032 825.1 filed on Jul. 11, 2008, the contents of which are hereby incorporated by reference.

BACKGROUND

The present invention relates to a pump in the style of a water-jet pump for creating a high vacuum.

For creating an ultra-high vacuum, turbomolecular pumps, cryopumps, sorption pumps, rotary plunger pumps, positive displacement pumps and jet pumps are used. As jet pumps, water-jet pumps or pumps based on oils as liquid are used. Only vacuum pressures which lie within the range of the vapor pressure of the liquid which is used can be achieved by these pumps. Therefore, known water-jet pumps and oil pumps can be used only as fore-pumps for creating a fore-vacuum, and for creating especially ultra-high vacuums have to be supplemented by downstream pumps such as turbo-molecular pumps. The pump systems which are constructed in this way are complex, expensive and labor-intensive in maintenance.

SUMMARY

It is one potential object to disclose a simply constructed pump with which vacuums into the ultra-high vacuum range are to be created. In particular, it is a potential object to disclose a pump with as few parts as possible, above all with few or no movable parts in order to be able to operate the pump in a wear-free and cost-effective manner, and with a simple way to create an ultra-high vacuum which is as beneficial as possible. In addition, a simple method for operating such a pump is to be disclosed.

The inventors propose a pump for creating a high vacuum, especially for creating an ultra-high vacuum, is to be constructed in the style of a water-jet pump or of a corresponding type. For this purpose, it comprises at least one chamber which is exposable to throughflow by a fluid in one flow direction. This chamber has at least one first feed for the fluid, which projects into the chamber and terminates in a nozzle orifice. In addition, the chamber has at least one outlet for the fluid, which is arranged opposite the nozzle orifice, as seen in the flow direction. Furthermore, the chamber has at least one second feed which leads into the chamber and is to be connected to a space which is to be evacuated. An ionic fluid is used as the fluid for such a pump.

In a preferred embodiment of the pump, provision is made for delivering the ionic fluid at a prespecified velocity and/or a prespecified pressure to the first feed, which preferably uses at least one feed pump.

The pump can preferably be connected to a closed fluid circuit or integrated into this, which comprises the feed pump for creating a fluid pressure in the at least one first fluid feed and which comprises a storage tank with a check valve for discharging gases, which storage tank is connected to the at least one fluid outlet and to the feed pump.

The ionic fluid which is to be provided for the pump may be a liquid and/or also a liquid-gas mixture. If applicable, a corresponding gas can also be used as fluid.

In this case, it is advantageous that with the pump the pressure in the space which is to be evacuated can be adjusted in dependence upon the ionic liquid which is used, especially upon the vapor pressure of the ionic liquid.

As ionic fluid, a fluid which contains sulfate ions, hydrogen sulfate ions, alkyl sulfate ions, thiocyanate ions, phosphate ions, borate ions, tetrakis hydrogen sulfate oborate ions, or silicate ions, is preferably selected.

Furthermore, the at least one second feed is preferably connected to an ultra-high vacuum chamber for an exchange or removal of gas between the ultra-high vacuum chamber and the at least one feed. As a result of the exchange of gas, an ultra-high vacuum, which lies within the pressure range of 10⁻⁷ to 10⁻¹² mbar, can be created in the ultra-high vacuum chamber.

In one preferred embodiment, the pressure in the ultra-high vacuum chamber is dependent upon the ionic liquid which is used, especially upon the vapor pressure of the ionic liquid.

In a further preferred embodiment, the at least one first fluid feed and/or the at least one second feed and/or the at least one fluid outlet are, or is, designed in the form of at least one pipe in each case.

The inventors also propose a method for operating the pump, which involves:

Creating a jet of fluid which flows through the chamber of the pump, drawing in gas in and/or into the chamber by the fluid jet, and discharging the gas from the chamber by the fluid jet. The steps in this case can be carried out in the stated sequence continuously at the same time or one after the other in pulses.

In a preferred embodiment of the operating method, the so-called Venturi effect is utilized by a corresponding design of the pump. In this way, high flow velocities of the fluid in the chamber and therefore particularly high negative pressures at the second feed are to be achieved which can lead to corresponding high vacuums into the range of ultra-high vacuums in a connected space which is to be evacuated.

The proposals aregenerally based on the idea that by the use of ionic fluids such as liquids in the specially designed jet pumps, a beneficial ultra-high vacuum can be created in a simple, reliable, low-wear and therefore inexpensive manner as a result of the low vapor pressure of such fluids, without the necessity of a large number of pump systems.

The previously mentioned advantages which are associated with the pump ensue for the operating method.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and advantages of the present invention will become more apparent and more readily appreciated from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 shows in a greatly schematized view a construction for creating an ultra-high vacuum with a jet pump.

FIG. 2 shows a detail of the chamber of the pump.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout.

In FIG. 1, the construction of a system 1 for creating especially an ultra-high vacuum HV is shown. The system 1 comprises a pump 2 with a first fluid feed 3 and a second feed 4 and also a fluid outlet 5. The pump 2 is integrated into a closed fluid circuit 9 which uses an ionic liquid as fluid F. The pump functions in the manner of a water-jet pump, wherein its operating medium, however, is not water but an ionic liquid or a corresponding liquid-gas mixture.

In the fluid circuit 9, the flow direction of the fluid F is identified by s. With regard to the flow direction, a feed pump 6 is connected upstream to the pump 2 and creates a high fluid pressure in at least one pipe-like section 9 a of the fluid circuit 9 upstream of the pump 2. Fluid F at a high flow velocity and/or at a high internal fluid pressure is therefore pumped by the feed pump 6 to the pump 2 via the section 9 a of a pipe system. The fluid F enters a chamber 11 of the pump 2 there via the first fluid feed 3. For this, the feed projects a little into the chamber and is designed there as a nozzle with a nozzle orifice 3 a (cf. FIG. 2). The fluid is sharply accelerated in the process. The acceleration is brought about according to the so-called Venturi effect on account of a corresponding design of the nozzle. The fluid flow velocity is increased for example tenfold to a hundred fold or thousand fold. Fluid flow velocities up to sonic speed are possible. The flow velocity is dependent upon the fluid pressure directly in front of the nozzle and upon the nozzle diameter in proportion to the piping diameter of the first fluid feed 3. The fluid jet, which discharges at high velocity from the nozzle at its orifice 3 a, absorbs portions of the gas which is in the chamber 11, for example as a result of impacts with the gas molecules and vortices as a result of friction in the gas in the chamber. The gas molecules which are entrained with the fluid flow discharge from the chamber 11 together with the fluid F at the fluid outlet 5 which lies opposite the nozzle orifice 3 a.

Via a section 9 b of the piping system, the fluid F which discharges from the chamber 11 via the fluid outlet 5 is directed into a storage tank 7. The fluid F is collected there and entrained gas molecules can escape from the fluid and, via a check valve 8, be discharged to the environment or into a further collecting tank. The collected fluid from the storage tank 7 can then be fed to the feed pump 6 by a further section 9 c of the piping system, with which a completed fluid circuit 9 in the piping system results.

In the chamber 11 of the pump 2, the gas molecules which are entrained and transported away with the fluid F lead to a negative pressure at a second feed 4 of the chamber 11 of the pump 2. A high-vacuum chamber 10 is connected to the second feed 4 of the pump chamber 11 via a piping system 12, for example a stainless steel pipe. Thus, an exchange or transporting of gas can take place between the high-vacuum chamber 10 and the pump chamber 11. The negative pressure which is created in the pump chamber 11 leads to a flow of gas, which gas can flow from a higher gas pressure in the high-vacuum chamber 10 to a lower gas pressure in the pump chamber 11. Only when a pressure balance has taken place, i.e. when the same gas pressure exists in the high-vacuum chamber 10 and in the pump chamber 11, does exchange of gas between the ultra-high vacuum chamber 10 and the pump chamber 11 no longer take place. The exchange of gas between the high-vacuum chamber 10 and the pump chamber 11 can therefore lead to a pressure drop in the high-vacuum chamber 10, i.e. gas is thus to be pumped out of the high-vacuum chamber 10 into the pump chamber 11.

With the described method, a gas pressure or a vacuum with a pressure which corresponds at least approximately to the vapor pressure of the fluid F which is used, can be created in the high-vacuum chamber 10. By using an ionic fluid as the operating medium of the pump 2, high-vacuum gas pressures can be achieved, i.e. a high vacuum in a high-vacuum chamber 10 which reaches into the ultra-high vacuum range of 10⁻⁷ to 10⁻¹² mbar.

Ionic fluids which are suited to the pump are known for example from “Angewandte Chemie” (Applied Chemistry), 2000, Volume 112, pages 3926 to 3945. According to this, liquids which at low temperatures, particularly at temperatures below 100° C., are melting salts with non-molecular, ionic character, are generally considered as such fluids. An especially advantageous property of such ionic liquids for use in the pump is that these have a practically non-measurable vapor pressure (at the usual application temperatures). Therefore, in spaces which are to be evacuated, negative pressures, which correspond to the vapor pressure of the liquids which are to be used, can be achieved. During operation of the pump, practically no liquid evaporates so that the drawn-in gas is easy to separate from the liquid.

Particularly suitable are fluids F (liquid or in a two-phase liquid-gas mixture) which contain sulfate ions, hydrogen sulfate ions, alkyl sulfate ions, thiocyanate ions, phosphate ions, borate ions, tetrakis hydrogen sulfate oborate ions, or silicate ions, at least as the chief portion (i.e. more than 50% by volume).

The invention has been described in detail with particular reference to preferred embodiments thereof and examples, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention covered by the claims which may include the phrase “at least one of A, B and C” as an alternative expression that means one or more of A, B and C may be used, contrary to the holding in Superguide v. DIRECTV, 69 USPQ2d 1865 (Fed. Cir. 2004). 

1-13. (canceled)
 14. A water-jet pump to create a high vacuum, comprising: an ionic fluid circulation fluid, the ionic fluid circulation fluid containing at least one of sulfate ions, hydrogen sulfate ions, alkyl sulfate ions, thiocyanate ions, phosphate ions, borate ions, tetrakis hydrogen sulfate oborate ions, and silicate ions; a chamber to communicate a through-flow of the circulation fluid; a first feed to supply the circulation fluid to the chamber, the first feed projecting into the chamber and terminating in a nozzle orifice, the nozzle orifice having at least a tenfold reduction in diameter relative to an upstream portion of the first feed; an outlet for the circulation fluid from the chamber, the outlet being positioned opposite to the nozzle orifice, in a flow direction; a second feed, which leads into the chamber and is connected to a space which is to be evacuated; a feed pump to deliver the circulation fluid into the first feed at a pre-specified velocity and/or at a pre-specified pressure; a storage tank with a check valve to discharge gases; and a closed fluid circuit to connect the feed pump to the first feed, to connect the outlet to the storage tank and to connect the storage tank to the feed pump.
 15. A water-jet pump to create a high vacuum, comprising: a chamber to communicate a fluid through-flow; a first feed to supply the fluid, which first feed projects into the chamber and terminates in a nozzle orifice; an outlet for the fluid from the chamber, the outlet being positioned opposite to the nozzle orifice, in a flow direction; and a second feed, which leads into the chamber and is connectable to a space which is to be evacuated, wherein the fluid is an ionic fluid.
 16. The pump as claimed in claim 15, further comprising means for delivering the ionic fluid into the first feed at a pre-specified velocity and/or at a pre-specified pressure.
 17. The pump as claimed in claim 15, further comprising a feed pump to deliver the ionic fluid into the first feed at a pre-specified velocity and/or at a pre-specified pressure.
 18. The pump as claimed in claim 17, further comprising: a storage tank with a check valve to discharge gases; and a closed fluid circuit to connect the feed pump to the first feed, to connect the outlet to the storage tank and to connect the storage tank to the feed pump.
 19. The pump as claimed in claim 15, wherein the ionic fluid is a liquid or a liquid-gas mixture.
 20. The pump as claimed in claim 19, wherein the pump creates a vacuum pressure reduction in the space to be evacuated, and the pressure reduction depends upon the vapor pressure of the ionic liquid.
 21. The pump as claimed in claim 15, wherein the ionic fluid contains at least one of sulfate ions, hydrogen sulfate ions, alkyl sulfate ions, thiocyanate ions, phosphate ions, borate ions, tetrakis hydrogen sulfate oborate ions, and silicate ions.
 22. The pump as claimed in claim 15, wherein the space to be evacuated is an ultra-high vacuum chamber, and gas is exchanged between the pump and the ultra-high vacuum chamber via the second feed.
 23. The pump as claimed in claim 22, wherein the pump created a vacuum pressure reduction in the space to be evacuated, and the vacuum pressure reduction reduces the pressure to a pressure range of 10⁻⁷ to 10⁻¹² mbar.
 24. The pump as claimed in claim 15, wherein piping is used to form at least one of the first feed, the second feed and the fluid outlet.
 25. A method for evacuating a space, comprising: providing a pump comprising: a chamber to communicate a ionic fluid through-flow; a first feed to supply the ionic fluid, which first feed projects into the chamber and terminates in a nozzle orifice; an outlet for the ionic fluid from the chamber, the outlet being positioned opposite to the nozzle orifice, in a flow direction; and a second feed, which leads into the chamber and is connectable to a space which is to be evacuated; creating a jet of ionic fluid through the chamber of the pump; drawing gas into the chamber with the jet of ionic fluid; and discharging the gas from the chamber with the jet of ionic fluid.
 26. The method as claimed in claim 25, wherein creating a jet, drawing gas, and discharging the gas are carried out in sequence, are carried out continuously at the same time, or are carried out in pulses.
 27. The method as claimed in claim 25, wherein the jet of ionic fluid is created using the Venturi effect. 